1. Unbalanced Forces & Motion

2. Balanced Forces Are forces that have a net force of zero Equal forces in opposite directions Balanced forces DO NOT change the motion of objects

3. Unbalanced Forces Has a net force that is not zero Unbalanced forces DO change the motion of objects Object Moves to the Left

4. What are forces that have a net force of zero called? a. Balanced b. Unbalanced c. Equal d. accelerating

5. What type of force allows you to stand up from a chair? a. Balanced b. Unbalanced c. Equal d. Opposite

6. A ball has two forces acting on it. One force is pushing it to the left, and a larger force is pushing it to the right. In which direction will the ball move? A. Right B. Left C. Up D. Down

7. Energy and Machines

8. Energy Is the capacity to do work Energy can be used to move muscles, operate machines, cook meals, and heat rooms. When you stand up, your body uses energy to hold itself up. Energy is needed to act against the force of gravity.

9. Machines Machines also use energy to act against gravity and friction. A machine is something that replaces human effort. Whenever a machine moves against the pull of gravity it uses energy.

10. Forms of Energy Heat energy, light energy, sound energy, electrical energy, chemical energy, and mechanical energy One form of energy can change into another form of energy. A light bulb changes electrical energy to light energy and heat energy.

11. Did you know? Some scientist have built machines that harness the energy from tides and waves. These machines turn the movement of water waves and tides into power that can be used to light nearby homes and businesses.

12. What is a device that replaces human effort? A. A chemical B. A machine C. A heater D. gravity

13. What is needed to operate a machine? a. Force b. Energy c. Lift d. Motion

14. Why does a machine that lifts boxes off the ground need energy? a. It needs energy to pull against the force of gravity. b. It needs energy to pull against an electrical force. c. It needs energy to pull against a chemical force. d. It needs energy to pull against a heat source.

15. Which kind of energy is shown in this illustration of a water wheel? a. Chemical energy b. Heat energy c. Light energy d. Mechanical energy